Hello John,
It wasn't clear from your opening post that you intened to stay with the same fuel or body shape and trim level, hence my posting.
If you scan the data pages you will find evidence that a whole host of apparently small differences between models can impact the towing capabilities.
So when asking for this type of advice its as well to provide enough information to be unambiguous.
Make
Model
Body type
Trim level
Engine fuel
Engine size (and tuning)
and Manufactured year
It may seem strange, but a model that spans several years of production in apprently the same Mk and trim level could have different towing limits, the manufacturer could have changed the clutch, or even the engine. For example Renault produced the phase three Espace from 1997 through to about 2003 with a 2.2 diesel. They changed the engine in mid model which changed the permitted towed weight limit. - same size engine, but from DT to DCI specification.
Any way I hope someone will be along to give their impressions.